1. Field of the Invention
The present invention relates to a magnetic disc unit and more particularly to a magnetic disc unit of the type using a magnetic disc cassette of which a hard casing contains a magnetic disc as magnetic recording medium having a center hub.
2. Description of the Prior Art
There have been known a magnetic disc cassette of the type in which a magnetic disc with a center hub is contained in a hard casing. A conventional magnetic disc unit which loads the magnetic disc cassette of the type described for recording or reproducing information therein or therefrom has the following various disadvantages.
In the conventional magnetic disc unit, after the magnetic disc cassette has been inserted into the magnetic disc unit, the magnetic disc is clamped by an additional operation of closing a door, rotating a lever or pushing a button. As a result, a large number of component parts are required, so that the magnetic disc unit is large in size and complicated in operation.
In the conventional magnetic disc unit, in order to clamp a magnetic disc, a center cone fits in a center hole of a center hub of the magnetic disc, and pushes the center hub against a spindle. As a result, one set of clamping mechanism is needed which clamps the magnetic disc. Therefore, the magnetic disc unit cannot be made compact in size or thin and its mechanism is complicated.
The conventional magnetic disc unit has one dust-proof door which is swingably attached to the cassette insertion opening. Such one dust-proof door results in a long radius of rotation when the door swings, so that a large space must be provided in order to allow the dust-proof door to swing, contrary to a recent tendency of making the magnetic disc unit more compact in size.
In order to solve this problem, there has been proposed a set of an upper dust-proof door and a lower dust-proof door, but unless the mating edges of the upper and lower dust-proof doors are spaced apart from each other by a small gap, they cannot be opened or closed, so that dust particles enter the inside of the magnetic disc unit through the gap between them.
In the conventional magnetic disc unit, photoswitches or microswitches are used to detect whether or not a magnetic disc cassette has properly been loaded at a suitable position. If the photoswitches are used, a light source and a photo detector must be disposed in opposite to each other, for example, in a vertical direction for the purpose of photo coupling, so that the magnetic disc unit become high and cannot be made compact in size. The same is true for microswitches.